Quartz crystal temperature transducer



Jan. 21, 1969 D. L. HAMMOND 3,423,609

QUARTZ CRYSTAL TEMPERATURE TRANSDUCER Filed Jan. 30, 1964 INVENTOR DONALD L. HAMMOND BY 9, M

AT TORNEY United States Patent 4 Claims This invention relates to a quartz crystal thermometer.

Quartz crystals change their resonance frequency with temperature. It has been proposed, therefore, to use them as thermometers: the quartz crystal is placed in the environment the temperature of which is to be measured, the resonance frequency of the crystal is measured and converted into a temperature reading. This conversion, however, presents a problem because the relationship between frequency and temperature is non-linear. For instance, the non-linearity of the quartz crystal thermometer described in the article entitled Quartz Crystal Thermometer for Measuring Temperature Deviation in the 10* to 10 C. Range, published in the February 1962 Review of Scientific Instruments, is of the order of 2%.

Over several hundred degrees centigrade, the relationship of temperature to frequency of quartz crystal resonators can be quite accurately represented by a third order expansion as follows:

In accordance with the present invention, a quartz crystal resonator is cut in such a fashion that the second and third order temperature coeflicients (B and C above) are each zero. A quartz crystal having a frequency which varies linearly with temperature is thus obtained.

It is the principal object of this invention to provide a quartz crystal the resonance frequency of which changes with temperature with a high degree of linearity.

The drawing shows a crystal in accordance with this invention.

Referring to the drawing, there is shown a crystal plate 5, together with its X-axis 7, its Y-axis 8 and its Z- axis 9. The orientation axis 12 of crystal plate relative to the crystallographic axes of quartz can be broadly defined using the Standards on Piezoelectric Crystals published in the Proceedings of the IRE for December 1949, on pp. 1378 to 1395. Using this terminology, the plate orientation is:

(yxwl):11.166+m120/9.393

where m=1, 2 or 3. Due to the symmetry of quartz, there are six such orientations having identical resonator properties, i.e. second and third order temperature coefficients equal to zero and a linear relationship with frequency. Thus the six orientations are:

"ice

(yxwl) 371.166/9.393 Where The orientations where m:3 may be expressed as follows (by subtracting 360):

In the specific embodiment shown in the drawing, the orientation of crystal plate 5 is specifically:

The crystal cut in accordance with the above definition has a frequency vs. temperature non-linearity which is less than .05%. As one departs from the two defined angles, the non-linearity increases. When the departure is one degree, the non-linearity is of the order of .5 Thus, in the following claims, the expression approximately is intended to cover a range of plus or minus one degree in each of the defined angles.

I claim:

1. A quartz crystal plate having an orientation of approximately (yxwl)i11.166+m120/9.393 where m is an integer not greater than 3.

2. A quartz crystal plate having an orientation of approximately (yxwl) 11.166/9.393.

3. A quartz crystal plate having an orientation of (yxwl):'11.166+ml20/9.393 where m is an integer not greater than 3.

4 A quartz crystal plate having an orientation of (yxwl)11.166/9.393.

References Cited UNITED STATES PATENTS 2,661,433 12/1953 Jafle 310-9 2,669,666 2/1954 lMason 3l09 2,554,332 5/1951 Iaffe 310-9 FOREIGN PATENTS 874,798 8/1961 Great Britain.

OTHER REFERENCES Electronic Design, May 10, 1966, article entitled A Guide to Crystal Selection by Otto Witz, pp. 48 to 51.

I D MILLER, Primary Examiner.

U.S. Cl. X.R. 310-89 

1. A QUARTZ CRYSTAL PLATE HAVING AN ORIENTATION OF APPROXIMATELY (YXWL)+-11.166*+M120*/9.393* WHERE M IS AN INTEGER NOT GREATER THAN
 3. 